Note on NatureScot’s considerations for development of marine mammal advice in relation to static gear fishing activities
Please note - The advice below was produced (January 2024) to assist the development of proposed management measures for fishing activity for MPAs and PMFs (11 most sensitive to bottom contact gear) outwith MPAs. Further considerations were made by Marine Directorate and the final proposed management measures being consulted upon in 2026 are available via Scottish Government’s website.
January 2024
Purpose
This note has been produced to provide an overview of the rationale for the static gear fisheries advice provided in NatureScot’s Conservation and Management Advice (CMA) documents for MPAs with the following species – harbour porpoise, Risso’s dolphin, minke whale, bottlenose dolphin, grey and harbour seals. It has been produced to assist with discussions with stakeholders who may ask about why there are differences in our advice between these species.
Development of fisheries advice for MPAs
Our management advice is captured in section 7 of the CMA documents. It is focused on the activities that cause an effect (a pressure) that a feature is sensitive to. Our advice takes a risk-based approach, i.e. we are focusing on providing advice where we believe there is a risk to achieving the Conservation Objectives. We have identified risks to achieving the Conservation Objectives where there is an overlap between protected features and activities associated with pressures that the features are sensitive to. We have provided management advice to support public authorities and others in managing these risks. Our advice is based on existing data and information on protected features and relevant activities and our understanding of the relationships between the features and activities. We have identified a range of management advice:
- management to remove or avoid pressures;
- management to reduce or limit pressures; or
- no additional management required.
Where reduce/limit advice has been provided it has been based on ecological advice/evidence about the interaction. For our advice on fisheries management we have also stated where we think this should be ‘considered’ or ‘recommended’. The term ‘considered’ is included to highlight that a fishery-feature interaction exists, but circumstances mean that a specific recommendation for action cannot / or need not be made at this point. However, there is sufficient cause to make fishery managers aware and for them to consider if a fishery management measure may be helpful in achieving the Conservation Objectives – particularly where there may be a synergy between the benefits of management actions for the fishery and the Conservation Objectives for the feature. The term ‘recommended’ highlights that a fishery-feature interaction exists, there is a reasonable evidence base and a specific recommendation can be made/ justified. We recognise that stakeholders can provide local environmental knowledge and more detailed information on activities, including in relation to intensity, frequency and methods. This additional information will help public authorities and others develop more specific management, focused on the interaction between features and activities.
In relation to marine mammals we have high confidence in the evidence base around the sensitivity of the species to static fishing gear. There is published literature of entanglement/bycatch in relation to marine mammals from the UK and Europe and also Scottish specific examples. We are in the process of getting sensitivity information for the marine mammal species finalised which will be entered into FeAST.
The development of marine mammal advice for each MPA was based on the sensitivity of the species to the pressures from gear, what we knew about the presence of those gear types within the site, and any evidence of interactions from bycatch and strandings information within Europe, UK and Scotland. The status of the protected features in the sites also form part of the evidence considered. Table 1 provides a summary of the evidence considered in the development of our advice for marine mammals in relation to static fishing gear.
We acknowledge that we have lower certainty in the intensity of fishing activity in each MPA and therefore the exact level of interaction and risk that maybe occurring within sites. This understanding should improve through stakeholder dialogue that Marine Directorate is leading and it can be taken into account in their development of management measures for sites.
| Species & MPA | NatureScot’s Conservation and Management Advice | Evidence considered in development of advice |
|---|---|---|
| Harbour porpoise, Inner Hebrides and the Minches SAC | Reduce or limit pressures Exclusion of the use of drift nets and nets set on the seabed (tangle, trammel, gill) to avoid the risk of entanglement/bycatch of harbour porpoise is recommended. Existing bycatch legislation and mitigation applies to certain fisheries. | Our advice considers the modelling (density) and sightings evidence at the time of designation and more recently (Paxton et al. unpublished, SCANS) indicates that harbour porpoise distribution and its population is stable (comparing SCANS III and early data from SCANS IV unpublished) across the west coast including the SAC and present throughout the year. It is a wide ranging species both within the SAC and beyond.
There is some set netting occurring within the SAC.
There has been bycatch in the wider ICES West of Scotland & Ireland (in gill nets). There have been limited stranding records that have been attributed to fisheries gear on the west coast and in the SAC from SMASS records (note that the gear type in the main not determined). Records: 1993 (salmon nets specified), 1999, 1997 2005, 2020 (this most recent record was located in Wester Ross).
We have advised that pressures associated with drift nets and set nets should be reduced/limited within the site – this should be achieved through managing the interaction through the exclusion of gear. There could be potential for the use of other mitigation e.g. pingers, vessel monitoring but the merits of these need to be considered further.
|
| Minke whale | Sea of the Hebrides Reduce or limit pressures
Southern Trench Reduce or limit pressures The further development and adoption of existing best practice to reduce or limit the risk of entanglement of minke whales in creel ropes and long lines is recommended. Exclusion of the use of drift nets and nets set on the seabed (tangle, trammel, gill) between June and October due to the risk of entanglement is recommended.
| Minke whale are a wide-ranging species, using coastal areas of east and west Scotland and offshore waters. The species are predominantly using the MPAs during April – October for feeding (see Sea of Hebrides CMA). More recent modelling and survey (Paxton et al. unpublished) supports previous modelling at the time designation in terms of minke whale use of the MPA and latest SCANS data indicates the minke whale population on the west coast appears to be stable.
We understand that some of these gear types are occurring in the MPA, e.g. set netting, creeling.
Entanglement represents the single most frequently documented cause of mortality for minke whales in Scottish waters (based on Scottish Marine Animal Stranding Scheme data 2012-2017). Leaper et al. (2022) estimate that 30 minke whales become entangled in creel gear each year in Scotland. Evidence shows that the majority of entanglements are caused by gill nets and creels. Photographic records report that 18% of minke whales on the west coast of Scotland show evidence of previous entanglement (Mathewson 2012).
We have advised that the reduce/limit advice for creeling and longlining to address entanglement is delivered through best practice guidance developed by the Scottish Entanglement Alliance (SEA). Results are due to be published on weighted lines and phase 2 of the work by SEA is being planned (but funding not confirmed).
Reduce/limit advice for drift and set nets could be achieved through seasonal spatial exclusion of the gear within the site.
|
| Risso’s dolphin | Reduce or limit pressures Exclusion of the use of drift nets and nets set on the seabed (tangle, trammel, gill) to avoid the risk of entanglement is recommended. | Risso’s dolphin are a wide-ranging species using coastal areas of the west coast and further offshore. Areas of higher density are off the east coast of Lewis. It is recorded in the MPA year round but a seasonal increase in sightings rates has been noted between May and October (Weir et al., 2019).
The density modelling and annual photo-ID survey work indicates interannual variability in usage of the MPA but overall predicted density distribution does not appear to have changed since the site designation and Paxton et al. (2014) density modelling work.
We understand that set netting is being used within the MPA and surrounding areas.
Two cases of bycatch have been established in this species from the 36 post mortem examinations (~ 5%) carried out between 2000 and 2017 through the UK Cetacean Strandings Investigation Programme (Deaville 2011; 2017), and there is one record of a Risso's bycaught in a set gillnet on the Celtic Shelf from the UK Bycatch Monitoring Programme. There are two records from SMASS database where death has been attributed as possibly being due to bycatch in nets (1993) on the west coast of Scotland, one being near Stornoway.
We have advised that pressures associated with drift nets and set nets should be reduced/limited within the site – this should be achieved through managing the interaction through the exclusion of gear potentially on a seasonal basis. There could be potential for the use of other mitigation e.g. pingers, vessel monitoring but the merits of these need to be considered further.
|
| Bottlenose dolphin | Remove or avoid pressures The exclusion of the use of drift nets and nets set on the seabed (tangle, trammel, gill) to avoid the risk of entanglement/bycatch of bottlenose dolphin is recommended. | The bottlenose dolphin population in the SAC is stable over the long-term with interannual variability in numbers. However, monitoring data from the last 6yr survey period 2017-2022 suggests that the estimated population using the SAC is declining (SCM 2024). Dolphins from the SAC range along the Coastal East Scotland Management Unit. The species on the east coast is far less wide ranging that other cetacean species. They are present in the SAC year round. More than 50% of the population on the east coast use the SAC in any given year and the frequency of use of the SAC (measured at 2 CPOD monitoring stations) is stable despite some inter-annual and seasonal variability. In the Tayside and Fife area bottlenose dolphins were encountered more often in and around the Tay estuary in waters less than 20 m deep and within 2 km of the coast. Bottlenose dolphins were also frequently encountered along the coast between Montrose and Aberdeen in waters less than 20 m deep and within 2 km of the coast (Quick et al. 2014).
Our understanding is that drift nets and set nets are not currently operating in the SAC.
Bottlenose dolphin have high sensitivity to bycatch in these gear types. Observational reports during the last decade (2011-2018) recorded a UK bycatch rate of one bottlenose dolphin per 6,292 hauls from predominantly offshore UK fixed gill net fisheries (Northridge et al., 2011-2018). There is only one record from SMASS database attributed to bycatch in proximity to the SAC (to the east).
We have advised the remove/avoid pressures associated with drift nets and set nets. We recommend that these fishing activities do not restart within the site.
|
| Grey seal and harbour seal | Reduce or limit pressures (entanglement) associated with the use of nets (including bottom set nets, drift nets and fyke nets)
| We have advised that pressures associated with drift nets and set nets should be reduced/limited within the site. This could be achieved through managing the interaction through the exclusion of gear and consideration could be given to temporal restrictions based on the most sensitive times of year (breeding, moulting).
The status of seal populations within management units and SACs varies around Scotland – some e.g. grey seals are doing well overall where as others, particularly harbour seal populations are in decline, due to various reasons (SCOS, 2022). This should be taken into account when developing measures.
SACs for seals have been designated for their importance as breeding, moulting and haul out locations. As such the boundaries are drawn around the specific areas of importance (unless there are other features) and therefore seal only SACs are relatively small. Whilst they can forage within the boundaries of the SACs they will normally travel notable distances to forage (between 20-100km but normally towards the shorter end).
The most recent estimate of bycatch of seals in UK fisheries was 356 animals in 2020 (95% CI 269-671). 81% of the bycatch estimate occurs in the south-west of the UK and most bycaught seals are young grey seals. Approximately 81% of the 2020 bycatch estimate occurs in the south-west, in ICES area 7, where the UK gillnet/trammel/ tangle net fishery is concentrated. The remainder occurs in area 4 which covers the North Sea and waters around Shetland and Orkney with less than 3% occurring in area 6 around the Hebrides and Northwest Scotland. Estimated bycatch in area 6 and area 4a was 46 seals (SCOS, 2022).
There are reports of seal bycatch in the tangle net fishery the Monach Isles (Marine Scotland, 2020) and around the Flannan Isles and St Kilda in a trial tangle net fishery (Strange, 1980).
|
References
Deaville, R. (2011:2017). Annual reports for the period 1st January to 31st December. UK Cetacean Strandings Investigation Programme (CSIP). http://ukstrandings.org/csip-reports/
Leaper, R., MacLennan, E., Brownlow, A., Calderan, S.V., Dyke, K., Evans, P.G.H., Hartny-Mills, L., Jarvis, D., McWhinnie, L., Philp, A., Read, F.L., Robinson, K.P. and Ryan, C. 2022. Estimates of humpback and minke whale entanglements in the Scottish static pot (creel) fishery. Endangered Species Research 49, 217–232.
Marine Scotland (2020). Phase 2 MPA measures and PMF review minutes: Stornoway – 12 March 2020. https://www.gov.scot/publications/phase-2-mpa-measures-and-pmf-review-minutes-stornoway-march-2020/
Mathewson, F. 2012. Non-lethal entanglement of minke whales (Balaenoptera acutorostrata) in fishing gear in the Hebrides. BSc thesis. University of St Andrews. 38pp.
Northridge, S., Kingston, A. and Thomas, L. (2011). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2010.
Northridge, S., Kingston, A. and Thomas, L. (2012). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2011.
Northridge, S., Kingston, A. and Thomas, L. (2013). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2012. AWFA Assessment Proforma v2, Assessment v2: March 2022 17
Northridge, S., Kingston, A. and Thomas, L. (2014). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2013.
Northridge, S., Kingston, A. and Thomas, L. (2015). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2014.
Northridge, S., Kingston, A. and Thomas, L. (2016). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2015.
Northridge, S., Kingston, A. and Thomas, L. (2017). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2016.
Northridge, S., Kingston, A. and Thomas, L. (2018). Annual report on the implementation of Council Regulation (EC) No 812/2004 during 2017.
(Reports available here - https://randd.defra.gov.uk/ProjectDetails?ProjectId=18535)
Quick, N. J., Arso, M., Cheney, B., Islas-Villanueva, V., Janik, V. M., Thompson, P. M., & Hammond, P. S. (2014). The east coast of Scotland bottlenose dolphin population: improving understanding of ecology outside the Moray Firth SAC. Report to DECC under offshore energy SEA programme. Document identifier URN: 14D/086
Scottish Marine Animal Stranding Scheme (SMASS) database. Accessed January 2024. https://strandings.org/map/
Special Committee on Seals (SCOS). 2022. Scientific Advice on Matters Related to the Management of Seal Populations: 2022. http://www.smru.st-andrews.ac.uk/files/2023/09/SCOS-2022.pdf
Strange, E. S. 1980. Gill net and tangle net fishing – Scottish Water summary report – all voyages. Working paper no. 80/23. Department of Agriculture and Fisheries for Scotland, Marine Laboratory, Aberdeen.
